Process for the preparation of tung oil



Patented Mar. 24, 1942 PROCESS FOR THE PREPARATION OF TUNG OIL Robert S. McKinney, Chevy Chase, and William Gordon Rose, College Park, lVId., and Andrew F. Freeman, Washington, D. C.

No Drawing. Application August 23, 1939, Serial No. 291,564

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 1 Claim.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed, if patented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to use of any royalty there- We hereby dedicate the invention herein described to the free use of the People in the territory of the United States to take effect on the granting of a patent to us.

Our invention relates. to a new process for the production of a clear, liquid, solvent-extracted tung oil from tung kernels and from tung oil press cake.

The principal object of our invention is to produce a solvent-extracted tung oil, which will not change to the solid phase after it has been prepared. The solvent extraction of tung oil from the tung kernels and tung oil press cake, because of the economies which are clearly evident from the almost complete removal of the oil, has been considered a great improvement over the pressing methods. However, attempts to prepare a commercially usable, solvent-extracted tung oil have been unsuccessful because the solvent-extracted tung oil, while initially clear, soon forms a solid. Upon standing, this solid becomes insoluble and infusible and this material is no longer usable in the Varnish kettle. This solidified tung oil is, therefore, not acceptable to the tung oil trade.

We have invented a process by which solventextracted tung oil is prepared from tung oil press cake, and from tung kernels, the resulting oils being liquid at ordinary temperatures. These liquid extracted oils, therefore, are acceptable to the tung oil trade and our process, because of its greater yield of oil, in comparison to the present pressing process, and because it yields a valuable oil and a superior fertilizer from the tung oil press cake, is of value to the industry.

We have found that when the oil is extracted from tung kernels, and from tung oil press cake, by a suitable solvent, such as we describe hereinafter, and the solvent-extracted oil is freed from solvent and subjected to a suitable heat treatment, the resulting oil is liquid and remains so. These oils are much superior to other solventextracted tung oils, in that they are liquid and, therefore, acceptable to the tung oil trade.

In carrying out our invention, the tung oil press cake, or the tung kernels, which have been separated from tung hulls and shells, are ground and rolled, to rupture the oil cells, allowing the subsequent removal of the tung oil, by the solvent. The ground and rolled tung kernels, or ground tung oil press cake, is subjected to the action of a petroleum solvent of a short boiling range, between room temperature and the boiling point of water. The extraction process is conducted, using the counter-current system, the fresh solvent first coming into contact with the partly extracted ground material. When the extraction process is completed, the oil-bearing solvent is filtered and then run to a still, where most of the solvent is removed by steam heat. The solventbearing oil is filtered and freed of remaining solvent by spraying it into a vacuum evaporator onto steam heated coils. Here the solvent-free oil is removed from. the bottom of the evaporator, while the solvent vapors are removed from the top of the evaporator. The. solvent-free tung oil is heated to 200 C., or higher, for a sufiicient time to yield a clear liquid oil.

Various apparatus may be used. to carry out our process of producing a clear, solvent-extracted, tung oil from tung kernels and from tung oil press cake. The following example is illustrative of the preferred manner in which our invention may be practiced:

Erample.A quantity of ground tung oil press cake, or tung kernels which have been separated from tung hulls and shells and ground and rolled, is subjected to the action of petroleum ether (boiling range to 138 F.) This extraction process is of the continuous percolation type, the fresh solvent running upon the bed of ground material. Upon completion of the extraction process, the oil-bearing solvent is filtered and run into a still, where the solution is heated preferably by a closed steam coil, thereby removing the bulk of the solvent. This concentrated solvent-bearing oil is filtered and then sprayed onto steam heated coils in a vacuum evaporator. Here the oil is freed of the remaining solvent and falls over the heated pipes to the bottom of the evaporator, while the solvent vapors are removed from the top of the evaporator and recovered by any suitable means. The solvent-free oil is heated to at least 200 C. for substantially 30 minutes, yielding an oil which remains clear and liquid at room temperature.

The solvent-extracted oil from the tung oil press cake when obtained by the first phase of the above method had the following characteristics: iodine value (Wijs) 160.0; time for Browne heat test, 15.5 minutes; solid at room temperature. The remainingv solvent-extracted oil from the tung oil press cake after it was heat-treated by the second phase had the following characteristics: iodine value (Wijs) 145.7; time of solidification with Browne heat test, 13 minutes; refractive index at 25, 1.5097; viscosity by Gardner standards=U=6.5 poises; liquid at room temperature.

When the solvent-extracted oil was obtained from tung kernels by the first phase of the foregoing method it had the following characteristics: iodine value (Wijs) 165.0; time of solidification with Browne heat test, 11% minutes; solid at room temperature. The remaining solventextracted oil from the tung kernels after it was heat-treated by the second phase had the following characteristics: iodine (Wijs) 152.5; time of solidification with Browne heat test, 11% minutes; liquid at room temperature.

Having thus described our invention, what we claim for Letters Patent is:

A process for producing a clear liquid petroleum ether solvent-extracted tung oil, which comprises subjecting petroleum ether solvent-extracted tung oil to a temperature of at least 200 C. for substantially 30 minutes.

ROBERT S. MCKINNEY. WILLIAM GORDON ROSE. ANDREW F. FREEMAN. 

